In recent years, specialized semiconductor process technologies have emerged for specific applications. Once such process is the Bipolar CMOS DMOS (BCD) process technology, which integrates semiconductor components manufactured according to a variety of process technologies (e.g., bipolar processes, CMOS processes and DMOS processes). The cost to manufacture integrated circuits according to BCD processes typically is substantially higher than to manufacture integrated circuits according to single process types (e.g., only bipolar processes, only CMOS processes or only DMOS process type). However, the costs to manufacture a circuit system as a single integrated circuit according to a BCD process can be commensurate with the cost to manufacture the same circuit system as three integrated circuits, each according to a single process type, and therefore BCD designs are attractive for various system designs.
Many system designs require an integrated circuit to handle voltages that, if misused, can damage the semiconductor components therein and render the integrated circuit unusable. Taking one example, an integrated circuit may be manufactured according to a process technology that can handle only 5V but some circuit components may be required to handle voltages at high levels such as 6-8V. Typical examples include power switching systems, which may drive components external to the integrated circuit. While some circuit designs have been developed to accommodate excess voltages (for example, a cascode configuration may enable a 5V device to function using a higher power supply voltage) such devices are still seldom used in such applications because the current through the power stages may be high and may cause damage to the switching elements. Another drawback of the prior configurations is the increased complexity and sensitivity of the power stage driver design. Due to the high cost of integrated circuits manufactured according to BCD processes, these risks are particularly acute because damage to a semiconductor component in BCD integrated circuits incurs a commensurately high replacement cost.
Accordingly, the inventor has identified a need for a cascode configuration that can be used in any process in which low voltage devices can be used sustain high voltage. For example, an improved Class D amplifier having increased power efficiency, less stress on amplifier components, and better EMI and SNR performance is provided.